Allergies usually don't occur with opioids of any type.
But all do have side effects such as itching, nausea, constipation, and initially drowsiness and respiratory depression. Some of the opioids cause more than others. Percodan (oxycodone and aspirin) does contain Aspirin which some people can have serious reactions such as severe asthma possibly death. Also, no Aspirin in those under 18 or so with fever..
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